(a+11)(a-9)=

Solution for (a+11)(a-9)= equation:

Simplifying
(a + 11)(a + -9) = 0

Reorder the terms:
(11 + a)(a + -9) = 0

Reorder the terms:
(11 + a)(-9 + a) = 0

Multiply (11 + a) * (-9 + a)
(11(-9 + a) + a(-9 + a)) = 0
((-9 * 11 + a * 11) + a(-9 + a)) = 0
((-99 + 11a) + a(-9 + a)) = 0
(-99 + 11a + (-9 * a + a * a)) = 0
(-99 + 11a + (-9a + a2)) = 0

Combine like terms: 11a + -9a = 2a
(-99 + 2a + a2) = 0

Solving
-99 + 2a + a2 = 0

Solving for variable 'a'.

Factor a trinomial.
(-11 + -1a)(9 + -1a) = 0

Subproblem 1
Set the factor '(-11 + -1a)' equal to zero and attempt to solve:

Simplifying
-11 + -1a = 0

Solving
-11 + -1a = 0

Move all terms containing a to the left, all other terms to the right.

Add '11' to each side of the equation.
-11 + 11 + -1a = 0 + 11

Combine like terms: -11 + 11 = 0
0 + -1a = 0 + 11
-1a = 0 + 11

Combine like terms: 0 + 11 = 11
-1a = 11

Divide each side by '-1'.
a = -11

Simplifying
a = -11
Subproblem 2
Set the factor '(9 + -1a)' equal to zero and attempt to solve:

Simplifying
9 + -1a = 0

Solving
9 + -1a = 0

Move all terms containing a to the left, all other terms to the right.

Add '-9' to each side of the equation.
9 + -9 + -1a = 0 + -9

Combine like terms: 9 + -9 = 0
0 + -1a = 0 + -9
-1a = 0 + -9

Combine like terms: 0 + -9 = -9
-1a = -9

Divide each side by '-1'.
a = 9

Simplifying
a = 9
Solution
a = {-11, 9}